As is known in the art, a heterostructure is a semiconductor junction having layers of dissimilar semiconductor material with unequal bandgaps and wherein carriers generated in one material fall into a quantum well or channel layer provided by the other material. As is also known in the art, over the last decade there has been considerable effort to develop semiconductors devices having gallium nitride (GaN) based channel layers electronics owing to GaN's high mobility, saturation velocity, breakdown field, chemical and thermal stability, and large band gap. These factors lead to power densities 10× that of gallium arsenide (GaAs) based devices, and make GaN the primary candidate for many power electronics applications. However, as military and commercial applications demand ever-higher power densities and operating temperatures, there becomes a need to explore new material systems that could satisfy these requirements. Diamond has the potential to be the material of choice for the next generation of power devices.
Diamond is comparable to or better than GaN in almost every category. Specifically, its electron and hole mobilities, band gap, breakdown voltage and thermal conductivity exceed that of GaN. In particular, the thermal conductivity of diamond (6-20 W cm−1° C.−1) is also noteworthy. At a typical output power density of 5 W/mm, the performance of GaN HEMTs is thermally degraded on current substrates even when grown on SiC (thermal conductivity of 3.6-4.9 W cm−1° C.−1 depending on polytype). However, the development of diamond based devices has been limited by the difficulty in growing single crystal diamond films or substrates, by the difficulty in growing n-type diamond, and the lack of heterojunctions with two dimensional gas confinement (2D gas) for high electron mobility transistor (HEMT) fabrication,